As government mandated fuel economy and emissions regulations continue to tighten, more pressure is being applied to vehicle manufacturers to find new technologies that increase fuel economy and minimize emissions from internal combustion engines. At the forefront of the new emissions and fuel economy technology is the electrification of the vehicle powertrain. Electricification enables sophisticated control options for powertrain components that are traditionally directly coupled to engine speed. Furthermore, hybridization is introducing new fuel conservation techniques such as start/stop technology.
These powertrain technology changes have a need for advanced thermal management systems. Engine and transmission friction, FEAD losses, engine warm-up, hot soak on shut-down, engine combustion efficiency, engine reliability, cabin comfort, battery efficiency, eMotor efficiency, inverter efficiency and many other parameters are directly or indirectly affected by the engine and powertrain thermal management. Moreover, electrification enables the adaptation of complex control systems in which individual powertrain components may be individually controlled, particularly relative to thermal management.
One of the areas in which thermal management systems can be productive relates to systems for driving cooling fans. Cooling fans have long been used in vehicle engine systems in order to pass air through a radiator in order to keep the engine coolant within acceptable temperature limits. The drives for these fans are an accessory to the engine and utilize power from the engine, thus affecting the power and gas mileage of the engine and vehicle.
It is an object of the present invention to provide an improved fan drive system which is an improvement over existing fan drive systems, particularly relative to increased fuel economy and reduction of undesirable emissions. It is also an object of the present invention to provide a hybrid fan drive system which allows operation of the fan drive both electrically and mechanically.